Light source device and projector

ABSTRACT

A light source device includes a light source that emits first and second excitation lights, a first wavelength conversion section including a first phosphor, and configured to convert the first excitation light into first fluorescence having a first wavelength band, a second wavelength conversion section including a second phosphor, and configured to convert the second excitation light into second fluorescence having a second wavelength band, and a light combining section that combines the first fluorescence and the second fluorescence. A first side surface of the first wavelength conversion section and a second side surface of the second wavelength conversion section are opposed to each other, the first fluorescence is emitted from a first end surface of the first wavelength conversion section toward the light combining section, and the second fluorescence is emitted from a first end surface of the second wavelength conversion section toward the light combining section.

The present application is based on, and claims priority from JPApplication Ser. No. 2018-142461, filed Jul. 30, 2018, the disclosure ofwhich is hereby incorporated by reference herein in its entirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a light source device and a projector.

2. Related Art

As a light source device used for a projector, there is proposed a lightsource device using fluorescence emitted from a phosphor whenirradiating the phosphor with excitation light emitted from a lightemitting element. In International Publication No. WO2006/054203(Document 1), there is disclosed a light source device which is providedwith a wavelength conversion member shaped like a flat plate, and alight emitting diode (LED) for emitting excitation light, and has aconfiguration of making the excitation light enter the wavelengthconversion member from a surface large in area, and emitting theconverted light from a surface small in area of the wavelengthconversion member.

As described in Document 1, by making the light emitted from the LEDenter the wavelength conversion member, it is possible to obtain lightdifferent in wavelength from the light emitted from the LED. Forexample, when the wavelength conversion member includes a yellowphosphor, it is possible to obtain yellow light from blue light emittedfrom the LED. However, in order to obtain white light necessary for alight source device for a projector, it is necessary to separatelyprovide a light source for emitting the blue light, and an opticalsystem such as a color combining element for combining the blue lightand the yellow light with each other in addition to the light sourcedevice of Document 1. As a result, there is a problem that the lightsource device grows in size. Further, also when obtaining colored lightother than the white light, there is a problem that the light sourcedevice grows in size due to the optical system for combining thefluorescence and other colored light with each other.

SUMMARY

Alight source device according to an aspect of the present disclosureincludes a light source configured to emit first excitation light andsecond excitation light, a first wavelength conversion section includinga first phosphor, and configured to convert the first excitation lightinto first fluorescence having a first wavelength band different from awavelength band of the first excitation light, a second wavelengthconversion section including a second phosphor, and configured toconvert the second excitation light into second fluorescence having asecond wavelength band different from a wavelength band of the secondexcitation light and the first wavelength band, and a light combiningsection configured to combine the first fluorescence emitted from thefirst wavelength conversion section and the second fluorescence emittedfrom the second wavelength conversion section with each other. The firstwavelength conversion section has a first end surface and a second endsurface opposed to each other, and a first side surface crossing thefirst end surface and the second end surface. The second wavelengthconversion section has a third end surface and a fourth end surfaceopposed to each other, and a second side surface crossing the third endsurface and the fourth end surface. The first side surface of the firstwavelength conversion section and the second side surface of the secondwavelength conversion section are opposed to each other. The firstfluorescence is emitted from the first end surface of the firstwavelength conversion section toward the light combining section, andthe second fluorescence is emitted from the third end surface of thesecond wavelength conversion section toward the light combining section.

In the light source device according to the aspect of the presentdisclosure, the first wavelength conversion section may have a thirdside surface crossing the first end surface and the second end surface,the second wavelength conversion section may have a fourth side surfacecrossing the third end surface and the fourth end surface, the firstexcitation light may enter the first wavelength conversion section fromthe third side surface of the first wavelength conversion section, andthe second excitation light may enter the second wavelength conversionsection from the fourth side surface of the second wavelength conversionsection.

In the light source device according to the aspect of the presentdisclosure, the light source may include a first light emitting diodedisposed so as to be opposed to the third side surface of the firstwavelength conversion section, and configured to emit the firstexcitation light, and a second light emitting diode disposed so as to beopposed to the fourth side surface of the second wavelength conversionsection, and configured to emit the second excitation light.

The light source device according to the aspect of the presentdisclosure may further include a control section configured toindividually control an intensity of the first excitation light to beemitted from the first light emitting diode and an intensity of thesecond excitation light emitted from the second light emitting diode.

In the light source device according to the aspect of the presentdisclosure, the light combining section may include a dichroic prismprovided to one of the first end surface of the first wavelengthconversion section and the third end surface of the second wavelengthconversion section, and having a dichroic mirror configured to reflectone of the first fluorescence and the second fluorescence and transmitthe other of the first fluorescence and the second fluorescence, and aprism provided to the other of the first end surface of the firstwavelength conversion section and the third end surface of the secondwavelength conversion section, and having a reflecting surfaceconfigured to reflect one of the first fluorescence and the secondfluorescence toward the dichroic prism.

In the light source device according to the aspect of the presentdisclosure, the dichroic prism may have contact with the third endsurface of the second wavelength conversion section.

In the light source device according to the aspect of the presentdisclosure, the prism may have contact with the first end surface of thefirst wavelength conversion section.

In the light source device according to the aspect of the presentdisclosure, the first side surface of the first wavelength conversionsection and the second side surface of the second wavelength conversionsection may be opposed to each other via an air layer.

In the light source device according to the aspect of the presentdisclosure, the first wavelength band may be a blue wavelength band, andthe second wavelength band may be a yellow wavelength band.

The light source device according to the aspect of the presentdisclosure may further include a third wavelength conversion sectionincluding a third phosphor, and configured to emit third fluorescencehaving a third wavelength band different from the first wavelength bandand the second wavelength band, wherein the light combining section maycombine the first fluorescence, the second fluorescence and the thirdfluorescence with each other.

In the light source device according to the aspect of the presentdisclosure, the light source may emit third excitation light, and thethird wavelength conversion section may convert the third excitationlight into the third fluorescence having the third wavelength banddifferent from a wavelength band of the third excitation light.

In the light source device according to the aspect of the presentdisclosure, the first wavelength band may be a blue wavelength band, thesecond wavelength band may be a green wavelength band and the thirdwavelength band may be a red wavelength band.

The light source device according to the aspect of the presentdisclosure may further include an angle conversion element which isdisposed at a light exit side of the light combining section, whichincludes an end surface of incidence of light and a light exit endsurface, and which makes a diffusion angle in the light exit end surfacesmaller than a diffusion angle in the end surface of incidence of light.

The light source device according to the aspect of the presentdisclosure may further include a reflective polarization elementdisposed at a light exit side of the light combining section, andconfigured to transmit light with a first polarization direction andreflect light with a second polarization direction different from thefirst polarization direction.

A light source device according to another aspect of the presentdisclosure includes a light source configured to emit light, a firstwavelength conversion section including a first phosphor, and configuredto convert the light emitted from the light source into firstfluorescence, and emit the first fluorescence from a first light exitsurface, a second wavelength conversion section disposed in parallel tothe first wavelength conversion section, including a second phosphor,and configured to convert the light emitted from the light source intosecond fluorescence, and emit the second fluorescence from a secondlight exit surface, a prism disposed so as to be opposed to the firstlight exit surface, and configured to reflect the first fluorescenceemitted from the first wavelength conversion section, and a dichroicprism disposed so as to be opposed to the prism and the second lightexit surface, and configured to combine the first fluorescence emittedfrom the prism and the second fluorescence emitted from the secondwavelength conversion section with each other to emit light obtained bycombining the first fluorescence and the second fluorescence with eachother, wherein the first fluorescence and the second fluorescence aredifferent in wavelength band from each other.

A projector according to another aspect of the present disclosureincludes the light source device according to any one of the aboveaspects of the present disclosure, a light modulation device configuredto modulate light from the light source device in accordance with imageinformation, and a projection optical device configured to project thelight modulated by the light modulation device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration diagram of a projector according toa first embodiment.

FIG. 2 is a schematic configuration diagram of a light source deviceaccording to the first embodiment.

FIG. 3 is a cross-sectional view of the light source device along theline shown in FIG. 2.

FIG. 4 is a cross-sectional view of the light source device along theline IV-IV shown in FIG. 2.

FIG. 5 is a cross-sectional view of a light source device according to amodified example of the first embodiment.

FIG. 6 is a schematic configuration diagram of a light source deviceaccording to a second embodiment.

FIG. 7 is a schematic configuration diagram of a light source deviceaccording to a third embodiment.

FIG. 8 is a schematic configuration diagram of a light source deviceaccording to a fourth embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS First Embodiment

Hereinafter, a first embodiment of the present disclosure will bedescribed using FIG. 1 through FIG. 5.

A projector according to the present embodiment is an example of aprojector using liquid crystal panels as light modulation devices.

It should be noted that in each of the drawings described below, theconstituents are shown with the scale ratios of respective sizes setdifferently between the constituents in some cases in order tofacilitate the visualization of each of the constituents.

FIG. 1 is a schematic configuration diagram of the projector 1 accordingto the first embodiment.

The projector 1 according to the first embodiment is a projection-typeimage display device for projecting a color image on a screen (aprojection target surface) SCR. The projector 1 uses three lightmodulation devices corresponding to respective colored light, namely redlight LR, green light LG and blue light LB.

As shown in FIG. 1, the projector 1 is provided with a light sourcedevice 2, a homogenous illumination optical system 40, a colorseparation optical system 3, a light modulation device 4R, a lightmodulation device 4G, a light modulation device 4B, a combining opticalsystem 5 and a projection optical device 6.

The light source device 2 emits illumination light WL toward thehomogenous illumination optical system 40. The detailed configuration ofthe light source device 2 will be described later in detail.

The homogenous illumination optical system 40 is provided with anintegrator optical system 31, a polarization conversion element 32 and asuperimposing optical system 33. The integrator optical system 31 isprovided with a first lens array 31 a and a second lens array 31 b. Thehomogenous illumination optical system 40 homogenizes the intensitydistribution of the illumination light WL emitted from the light sourcedevice 2 in each of the light modulation device 4R, the light modulationdevice 4G and the light modulation device 4B as illumination targetareas. The illumination light WL having been emitted from the homogenousillumination optical system 40 enters the color separation opticalsystem 3.

The color separation optical system 3 separates the illumination lightWL as white light into the red light LR, the green light LG and the bluelight LB. The color separation optical system 3 is provided with a firstdichroic mirror 7 a, a second dichroic mirror 7 b, a first reflectingmirror 8 a, a second reflecting mirror 8 b, a third reflecting mirror 8c, a first relay lens 9 a and a second relay lens 9 b.

The first dichroic mirror 7 a separates the illumination light WL fromthe light source device 2 into the red light LR and the other light (thegreen light LG and the blue light LB). The first dichroic mirror 7 atransmits the red light LR thus separated from, and at the same timereflects the other light (the green light LG and the blue light LB).Meanwhile, the second dichroic mirror 7 b separates the other light intothe green light LG and the blue light LB. The second dichroic mirror 7 breflects the green light LG thus separated from and transmits the bluelight LB.

The first reflecting mirror 8 a is disposed in the light path of the redlight LR, and reflects the red light LR, which has been transmittedthrough the first dichroic mirror 7 a, toward the light modulationdevice 4R. Meanwhile, the second reflecting mirror 8 b and the thirdreflecting mirror 8 c are disposed in the light path of the blue lightLB, and reflect the blue light LB, which has been transmitted throughthe second dichroic mirror 7 b, toward the light modulation device 4B.Further, the green light LG is reflected by the second dichroic mirror 7b toward the light modulation device 4G.

The first relay lens 9 a and the second relay lens 9 b are disposed atthe light exit side of the second dichroic mirror 7 b in the light pathof the blue light LB. The first relay lens 9 a and the second relay lens9 b correct a difference in illuminance distribution of the blue lightLB due to the fact that the blue light LB is longer in optical pathlength than the red light LR and the green light LG.

The light modulation device 4R modulates the red light LR in accordancewith image information to form image light corresponding to the redlight LR. The light modulation device 4G modulates the green light LG inaccordance with the image information to form image light correspondingto the green light LG. The light modulation device 4B modulates the bluelight LB in accordance with the image information to form image lightcorresponding to the blue light LB.

As the light modulation device 4R, the light modulation device 4G andthe light modulation device 4B, there are used, for example,transmissive liquid crystal panels. Further, on the incident side andthe exit side of the liquid crystal panel, there are disposedpolarization plates (not shown), respectively, and thus, there is formeda configuration of transmitting only the linearly polarized light with aspecific direction.

On the incident side of the light modulation device 4R, the lightmodulation device 4G and the light modulation device 4B, there aredisposed a field lens 10R, a field lens 10G and a field lens 10B,respectively. The field lens 10R, the field lens 10G and the field lens10B collimate principal rays of the red light LR, the green light LG andthe blue light LB entering the light modulation device 4R, the lightmodulation device 4G and the light modulation device 4B, respectively.

The combining optical system 5 combines the image light corresponding tothe red light LR, the image light corresponding to the green light LGand the image light corresponding to the blue light LB with each otherin response to incidence of the image light respectively emitted fromthe light modulation device 4R, the light modulation device 4G and thelight modulation device 4B, and then emits the image light thus combinedtoward the projection optical device 6. As the combining optical system5, there is used, for example, a cross dichroic prism.

The projection optical device 6 is constituted by a plurality ofprojection lenses. The projection optical device 6 projects the imagelight having been combined by the combining optical system 5 toward thescreen SCR in an enlarged manner. Thus, an image is displayed on thescreen SCR.

The light source device 2 will hereinafter be described.

FIG. 2 is a schematic configuration diagram of the light source device2. FIG. 3 is a cross-sectional view of the light source device 2 alongthe line shown in FIG. 2. FIG. 4 is a cross-sectional view of the lightsource device 2 along the line IV-IV shown in FIG. 2.

As shown in FIG. 2, the light source device 2 is provided with a firstwavelength conversion rod 51 (a first wavelength conversion section), asecond wavelength conversion rod 52 (a second wavelength conversionsection), a light source 54, a light combining section 55, an angleconversion element 56, a collimator lens 57 and a control section 58.

As shown in FIG. 2 and FIG. 3, the first wavelength conversion rod 51has a quadrangular prismatic shape, and has a first end surface 51 a anda second end surface 51 b opposed to each other, and four side surfaces51 c 1, 51 c 2, 51 c 3 and 51 c 4 crossing the first end surface 51 aand the second end surface 51 b. The whole of the side surfaceconstituted by the four side surfaces 51 c 1, 51 c 2, 51 c 3 and 51 c 4corresponds to a first side surface in the appended claims.

As shown in FIG. 2 and FIG. 4, the second wavelength conversion rod 52has a quadrangular prismatic shape, and has a third end surface 52 a anda fourth end surface 52 b opposed to each other, and four side surfaces52 c 1, 52 c 2, 52 c 3 and 52 c 4 crossing the third end surface 52 aand the fourth end surface 52 b. The whole of the side surfaceconstituted by the four side surfaces 52 c 1, 52 c 2, 52 c 3 and 52 c 4corresponds to a second side surface in the appended claims. An axispassing through the center of the third end surface 52 a and the centerof the fourth end surface 52 b of the second wavelength conversion rod52 is defined as an optical axis J1 of the light source device 2. Thelight from the light source device 2 is emitted in a direction of theoptical axis J1.

In the present embodiment, the first wavelength conversion rod 51 andthe second wavelength conversion rod 52 have substantially the samedimensions. The length A in the longitudinal direction (a normaldirection of the first end surface 51 a) of the first wavelengthconversion rod 51 is longer than the length B in the width direction (anormal direction of the side surface 51 c 1) of the first wavelengthconversion rod 51. For example, the length A is about ten throughseveral tens times as large as the length B. Substantially the same asthe first wavelength conversion rod 51 applies also to the secondwavelength rod 52.

It should be noted that each of the first wavelength conversion rod 51and the second wavelength conversion rod 52 is not necessarily requiredto have the quadrangular prismatic shape, but can also have anotherpolygonal shape such as a triangular prismatic shape. Alternatively, itis also possible for each of the first wavelength conversion rod 51 andthe second wavelength conversion rod 52 to have a columnar shape. Wheneach of the first wavelength conversion rod 51 and the second wavelengthconversion rod 52 has a columnar shape, the first wavelength conversionrod 51 has a first end surface and a second end surface parallel to eachother, and one side surface perpendicular to the first end surface andthe second end surface. The second wavelength conversion rod 52 has athird end surface and a fourth end surface parallel to each other, andone side surface perpendicular to the third end surface and the fourthend surface.

The first wavelength conversion rod 51 and the second wavelengthconversion rod 52 are disposed at a distance in an orientation in whichthe side surface 51 c 1 of the first wavelength conversion rod 51 andthe side surface 52 c 1 of the second wavelength conversion rod 52 areopposed to each other. In other words, the side surface 51 c 1 of thefirst wavelength conversion rod 51 and the side surface 52 c 1 of thesecond wavelength conversion rod 52 are opposed to each other via an airlayer. In other words, the first wavelength conversion rod 51 and thesecond wavelength conversion rod 52 are arranged in parallel to eachother.

Hereinafter, for the sake of convenience of explanation, the end surfaceon the side where the light is emitted from the first wavelengthconversion rod 51 is referred to as the first end surface 51 a, and theend surface facing to the opposite side to the first end surface 51 a isreferred to as the second end surface 51 b. Further, the end surface onthe side where the light is emitted from the second wavelengthconversion rod is referred to as the third end surface 52 a, and the endsurface facing to the opposite side to the third end surface 52 a isreferred to as the fourth end surface 52 b.

As shown in FIG. 3 and FIG. 4, the light source 54 is provided with afirst light source 541 and a second light source 542. As shown in FIG.2, the first light source 541 is disposed so as to straddle the sidesurface 51 c 3 of the first wavelength conversion rod 51 and the sidesurface 52 c 3 of the second wavelength conversion rod 52. The secondlight source 542 is disposed so as to straddle the side surface 51 c 4of the first wavelength conversion rod 51 and the side surface 52 c 4 ofthe second wavelength conversion rod 52. The light source 54 emits firstexcitation light and second excitation light. The side surface 51 c 3and the side surface 51 c 4 of the first wavelength conversion rod 51correspond to a third side surface of the appended claims. Further, theside surface 52 c 3 and the side surface 52 c 4 of the second wavelengthconversion rod 52 correspond to a fourth side surface of the appendedclaims.

The first light source 541 and the second light source 542 have the sameconfiguration, and are each provided with a substrate 543, and aplurality of light emitting diodes 61, 62 (LED) mounted on one surfaceof the substrate 543, the one surface being opposed to the firstwavelength conversion rod 51 and the second wavelength conversion rod52. In the present embodiment, each of the light sources is providedwith the 12 LED 61, 62, but the number of the LED 61, 62 is notparticularly limited. The LED 61 each emit the first excitation light.The LED 62 each emit the second excitation light. The wavelength band ofthe first excitation light and the second excitation light is anultraviolet wavelength band, a violet wavelength band or a bluewavelength band in range of, for example, about 200 nm through 495 nm.It should be noted that each of the light sources 541, 542 can also beprovided with other optical members such as a light guide plate, adiffusion plate or a lens besides the substrate 543 and the LED 61, 62.

The plurality of LED 61 is disposed so as to be opposed to the sidesurface 51 c 3 and the side surface 51 c 4 of the first wavelengthconversion rod 51, and the plurality of LED 62 is disposed so as to beopposed to the side surface 52 c 3 and the side surface 52 c 4 of thesecond wavelength conversion rod 52. As shown in FIG. 2, the pluralityof LED 61, 62 is arranged in two columns. Some (six) LED 61 are arrangedalong the longitudinal direction of the first wavelength conversion rod51, and the remaining (six) LED 62 are arranged along the longitudinaldirection of the second wavelength conversion rod 52. Hereinafter, theLED 61 arranged along the longitudinal direction of the first wavelengthconversion rod 51 are referred to as first LED 61, and the LED 62arranged along the longitudinal direction of the second wavelengthconversion rod 52 are referred to as second LED 62.

The first excitation light El for exciting a first phosphor included inthe first wavelength conversion rod 51 is emitted form the first LED 61.Meanwhile, the second excitation light E2 for exciting a second phosphorincluded in the second wavelength conversion rod 52 is emitted form thesecond LED 62. As described above, the first excitation light El emittedfrom the first LED 61 and the second excitation light E2 emitted fromthe second LED 62 are different in phosphor to excite from each other.Therefore, the first excitation light El and the second excitation lightE2 can have respective wavelength bands which are optimized for thephosphors of the respective wavelength conversion rods 51, 52, and aretherefore different from each other, or can also have the samewavelength band commonly used as the excitation light for either of thephosphors.

In the present embodiment, the light source 54 has the first LED 61 foremitting the first excitation light E1 in the ultraviolet wavelengthband, and the second LED 62 for emitting the second excitation light E2in the blue wavelength band.

As shown in FIG. 3, the first LED 61 are disposed so as to be opposed tothe side surface 51 c 3 and the side surface 51 c 4 of the firstwavelength conversion rod 51, and emit the first excitation light E1 inthe first excitation wavelength band toward the side surface 51 c 3 andthe side surface 51 c 4. The first excitation wavelength band is theultraviolet wavelength band of, for example, 200 nm through 380 nm. Itshould be noted that the first excitation wavelength band can also be aviolet wavelength band of, for example, around 400 nm. The firstexcitation light E1 enters the first wavelength conversion rod 51 fromthe side surface 51 c 3 and the side surface 51 c 4 of the firstwavelength conversion rod 51.

As shown in FIG. 4, the second LED 62 are disposed so as to be opposedto the side surface 52 c 3 and the side surface 52 c 4 of the secondwavelength conversion rod 52, and emit the second excitation light E2 inthe second excitation wavelength band toward the side surface 52 c 3 andthe side surface 52 c 4. The second excitation wavelength band is theblue wavelength band of, for example, 450 nm through 495 nm. It shouldbe noted that the second excitation wavelength band can also be theultraviolet wavelength band of, for example, 200 nm through 380 nm, orcan also be the violet wavelength band of, for example, around 400 nm.The second excitation light E2 enters the second wavelength conversionrod 52 from the side surface 52 c 3 and the side surface 52 c 4 of thesecond wavelength conversion rod 52.

The first wavelength conversion rod 51 is formed of, for example,fluorescent glass obtained by dispersing rare-earth ions in the glass,or a material obtained by dispersing blue phosphor in a binder such asglass or resin. Specifically, as the fluorescent glass, there is usedLumilass (a trade name; made by Sumita Optical Glass, Inc.) or the like.As the blue phosphor (the first phosphor), there is used, for example,BaMgAl₁₀O₁₇:Eu(II). The first wavelength conversion rod 51 converts thefirst excitation light E1 into first fluorescence KB (blue light) in afirst wavelength band. The first wavelength band is the blue wavelengthband of, for example, 450 through 495 nm. The first fluorescence KB isemitted from the first end surface 51 a of the first wavelengthconversion rod 51 toward the light combining section 55.

The second wavelength conversion rod 52 is formed of a ceramic phosphor(polycrystalline phosphor) for converting the wavelength of the secondexcitation light E2 into the wavelength of second fluorescence KY in asecond wavelength band. The second wavelength band is a yellowwavelength band of, for example, 490 through 750 nm. The secondwavelength conversion rod 52 can also be formed of a single-crystalphosphor instead of the polycrystalline phosphor. Alternatively, thesecond wavelength conversion rod 52 can also be formed of fluorescentglass. Alternatively, the second wavelength conversion rod 52 can alsobe formed of a material obtained by dispersing a number of phosphorparticles in a binder made of glass or resin. The second fluorescence KYis emitted from the third end surface 52 a of the second wavelengthconversion rod 52 toward the light combining section 55.

The second wavelength conversion rod 52 includes, for example, anyttrium aluminum garnet (YAG) phosphor as the yellow phosphor (thesecond phosphor). Citing YAG:Ce including cerium (Ce) as an activatoragent as an example, as the material of the second wavelength conversionrod 52, there can be used a material obtained by mixing raw powderincluding constituent elements such as Y₂O₃, Al₂O₃ and CeO₃ to cause thesolid-phase reaction, Y—Al—O amorphous particles obtained by a wetprocess such as a coprecipitation process or a sol-gel process, and YAGparticles obtained by a gas-phase process such as a spray dryingprocess, a flame heat decomposition process or a thermal plasma process.

The first wavelength conversion rod 51 has a mirror disposed on thesecond end surface 51 b of the first wavelength conversion rod 51. Thesecond wavelength conversion rod 52 has the mirror 63 disposed on thefourth end surface 52 b of the second wavelength conversion rod 52.Although in the present embodiment, the common mirror 63 is disposed soas to straddle the first wavelength conversion rod 51 and the secondwavelength conversion rod 52 as shown in FIG. 2, it is also possible toprovide the mirror 63 individually to the first wavelength conversionrod 51 and the second wavelength conversion rod 52. The mirror 63 isformed of a metal film or a dielectric multilayer film.

As shown in FIG. 2, the light combining section 55 is provided with adichroic prism 65 and a prism 66. The dichroic prism 65 has contact withthe third end surface 52 a of the second wavelength conversion rod 52.The dichroic prism has a dichroic mirror 65 m for reflecting the firstfluorescence KB and transmitting the second fluorescence KY. The prism66 has contact with the first end surface 51 a of the first wavelengthconversion rod 51. The prism 66 has a reflecting surface 66 f forreflecting the first fluorescence KB toward the dichroic prism 65.

The prism 66 is formed of a prism shaped like a triangular prism havingan isosceles right triangular cross-sectional shape, and has an endsurface of incidence of light 66 a, a reflecting surface 66 f and alight exit end surface 66 b. The prism 66 has a function of folding thelight path of the first fluorescence KB, which has entered the prism 66,at an angle of 90° and then emitting the first fluorescence

KB. In other words, the prism 66 reflects the first fluorescence KB,which has been emitted from the first end surface 51 a of the firstwavelength conversion rod 51, with the reflecting surface 66 f tothereby fold the light path, and then emits the first fluorescence KBfrom the light exit end surface 66 b. It should be noted that it is alsopossible to apply a reflecting plate having an equivalent function tothe present disclosure as a substitute of the prism 66.

The dichroic prism 65 is disposed so as to be opposed to the light exitend surface 66 b of the prism 66 and the third end surface 52 a of thesecond wavelength conversion rod 52. The dichroic prism 65 has contactwith the third end surface 52 a of the second wavelength conversion rod52. The dichroic prism 65 has a rectangular solid shape, and has an endsurface of incidence of light 65 a, an end surface of incidence of light65 b, and a light exit end surface 65 c. The dichroic mirror 65 m has aproperty of reflecting light in the blue wavelength band whiletransmitting light in the yellow wavelength band. Thus, the dichroicprism 65 combines the first fluorescence KB emitted from the first endsurface 51 a of the first wavelength conversion rod 51 and the secondfluorescence KY emitted from the third end surface 52 a of the secondwavelength conversion rod 52 with each other. The composite light KW asthe white light consisting of the first fluorescence KB as the bluefluorescence and the second fluorescence KY as the yellow fluorescenceis emitted from the light combining section 55.

The angle conversion element 56 is disposed at the light exit side ofthe light exit end surface 65 c of the dichroic prism 65. The angleconversion element 56 is formed of a taper rod having an end surface ofincidence of light 56 a which the composite light KW enters, and a lightexit end surface 56 b from which the composite light KW is emitted. Theangle conversion element 56 has a truncated quadrangular pyramid shape,and the cross-sectional area perpendicular to the optical axis J1increases along the proceeding direction of the composite light KW, andthe area of the light exit end surface 56 b is larger than the area ofthe end surface of incidence of light 56 a. Thus, the composite light KWchanges the angle to the direction parallel to the optical axis J1 everytime the composite light KW is totally reflected by side surface 56 cwhile proceeding inside the angle conversion element 56. In such amanner, the angle conversion element 56 makes the diffusion angle of thecomposite light KW in the light exit end surface 56 b smaller than thediffusion angle of the composite light KW in the end surface ofincidence of light 56 a.

The angle conversion element 56 is fixed to the dichroic prism 65 sothat the end surface of incidence of light 56 a is opposed to the lightexit end surface 65 c of the dichroic prism 65. Specifically, the angleconversion element 56 and the dichroic prism 65 have contact with eachother via an optical adhesive (not shown), and no air gap (no air layer)is disposed between the angle conversion element 56 and the dichroicprism 65. It should be noted that the angle conversion element 56 canalso be fixed so as to have direct contact with the dichroic prism 65by, for example, an arbitrary support member. In any case, it isdesirable that no air gap exists between the angle conversion element 56and the dichroic prism 65. It is desirable to make the refractive indexof the angle conversion element 56 and the refractive index of thedichroic prism 65 coincide with each other as precise as possible.

It should be noted that it is also possible to use a compound parabolicconcentrator (CPC) as the angle conversion element 56 instead of thetaper rod. When using the CPC as the angle conversion element 56, it isalso possible to obtain substantially the same advantages as those whenusing the taper rod.

The collimator lens 57 is disposed at the light exit side of the lightexit end surface 56 b of the angle conversion element 56. The collimatorlens 57 collimates the composite light KW emitted from the angleconversion element 56. Therefore, parallelism of the composite light KWthe angle distribution of which is converted by the angle conversionelement 56 is further improved by the collimator lens 57. The collimatorlens 57 is formed of a convex lens. It should be noted that whensufficient parallelism is obtained by the angle conversion element 56alone, it is not necessarily required to provide the collimator lens 57.

The control section 58 controls the power to be supplied to the firstLED 61 and the second LED 62 to thereby individually control theintensity of the first excitation light El emitted from the first LED 61and the intensity of the second excitation light E2 emitted from thesecond LED 62.

The light source device 2 according to the present disclosure isprovided with the light source 54, the first wavelength conversion rod51 (the first wavelength conversion section), the second wavelengthconversion rod 52 (the second wavelength conversion section), the prism66 and the dichroic prism 65, wherein the light source 54 emits thelight, the first wavelength conversion rod 51 includes the firstphosphor, converts the light emitted from the light source 54 into thefirst fluorescence KB, and then emits the first fluorescence KB from thefirst end surface 51 a (a first light exit surface), the secondwavelength conversion rod 52 is disposed in parallel to the firstwavelength conversion rod 51, includes the second phosphor, converts thelight emitted from the light source 54 into the second fluorescence KY,and then emits the second fluorescence KY from the third end surface 52a (a second light exit surface), the prism 66 is disposed so as to beopposed to the first end surface 51 a to reflect the first fluorescence

KB emitted from the first wavelength conversion rod 51, the dichroicprism 65 is disposed so as to be opposed to the prism 66 and the thirdend surface 52 a, and combines the first fluorescence KB emitted fromthe prism 66 and the second fluorescence KY emitted from the secondwavelength conversion rod 52 with each other to emit the result, and thewavelength band of the first fluorescence KB and the wavelength band ofthe second fluorescence KY are different from each other.

Hereinafter, the behavior of the light in the light source device 2having the configuration described above will be described.

As shown in FIG. 3, when the first excitation light El having beenemitted from the first LED 61 enters the first wavelength conversion rod51, the first phosphor included in the first wavelength conversion rod51 is excited, and the first fluorescence KB is emitted from anarbitrary light emitting point Pl. The first fluorescence KB proceedsfrom the arbitrary light emitting point P1 toward all directions, andthe first fluorescence KB proceeding toward the side surface proceedstoward the first end surface 51 a or the second end surface 51 b whilerepeating the total reflection by the side surfaces. The firstfluorescence KB having proceeded toward the first end surface 51 aenters the prism 66. Meanwhile, the first fluorescence KB havingproceeded toward the second end surface 51 b is reflected by the mirror63, and thus, the light path thereof is folded back, and then the firstfluorescence KB proceeds toward the first end surface 51 a.

Subsequently, as shown in FIG. 12, the first fluorescence KB, which hasbeen emitted from the first end surface 51 a of the first wavelengthconversion rod 51, is reflected by the reflecting surface 66 f of theprism 66, and thus, the light path thereof is folded, and then the firstfluorescence KB enters the dichroic prism 65. It should be noted that itis desirable that a gap (an air layer) is provided between the prism 66and the dichroic prism 65 so that the prism 66 and the dichroic prism 65do not have direct contact with each other. By providing the gap betweenthe prism 66 and the dichroic prism 65, the light small in incidentangle out of the light having proceeded to the vicinity of the boundarybetween the prism 66 and the dichroic prism 65 can be prevented fromfailing to reach the dichroic mirror 65 m and being leaked outside fromthe side surfaces of the angle conversion element 56. Further it ispossible to prevent the second fluorescence KY from proceeding towardthe prism 66, and thus, it is possible to improve the light useefficiency with respect to the second fluorescence KY. It should benoted that when giving higher priority to the use efficiency of thefirst fluorescence KB than the use efficiency of the second fluorescenceKY, it is also possible to dispose a member such as glass between theprism 66 and the dichroic prism 65. According to this configuration,internal total reflection of the first fluorescence KB occurs betweenthe prism 66 and the dichroic prism 65, and thus, it is possible torecursively guide the light returning to the first wavelength conversionrod 51 to the dichroic prism 65 side.

Meanwhile, as shown in FIG. 4, when the second excitation light E2having been emitted from the second LED 62 enters the second wavelengthconversion rod 52, the second phosphor included in the second wavelengthconversion rod 52 is excited, and the second fluorescence KY is emittedfrom an arbitrary light emitting point P2. The second fluorescence KYproceeds from the arbitrary light emitting point P2 toward alldirections, and the second fluorescence KY proceeding toward the sidesurfaces proceeds toward the third end surface 52 a or the fourth endsurface 52 b while repeating the total reflection by the side surfaces.The second fluorescence KY having proceeded toward the third end surface52 a enters the dichroic prism 65 from the third end surface 52 a.Meanwhile, the second fluorescence KY having proceeded toward the fourthend surface 52 b is reflected by the mirror 63, and thus, the light paththereof is folded back, and then the second fluorescence KY proceedstoward the third end surface 52 a.

As shown in FIG. 2, the first fluorescence KB having entered thedichroic prism 65 is reflected by the dichroic mirror 65 m. Meanwhile,the second fluorescence KY having entered the dichroic prism 65 istransmitted through the dichroic mirror 65 m. As a result, the firstfluorescence KB as the blue fluorescence and the second fluorescence KYas the yellow fluorescence are combined with each other, and thecomposite light KW as the white light is emitted from the light exit endsurface 65 c of the dichroic prism 65. The composite light KW havingbeen emitted from the dichroic prism 65 is collimated by the angleconversion element 56 and the collimator lens 57, and is then emittedfrom the light source device 2. The composite light KW (the illuminationlight WL) having been emitted from the light source device 2 proceedstoward the integrator optical system 31 as shown in FIG. 1.

In the light source device 2 according to the present embodiment, thefirst wavelength conversion rod 51 for emitting the first fluorescenceKB and the second wavelength conversion rod 52 for emitting the secondfluorescence KY are disposed so that the side surfaces 51 c 1, 52 c 1are opposed to each other. Further, the dichroic prism 65 is disposed onthe third end surface 52 a of the second wavelength conversion rod 52.Further, the first light source 541 is disposed at the position opposedto the side surface 51 c 3 of the first wavelength conversion rod 51 andthe side surface 52 c 3 of the second wavelength conversion rod 52, andthe second light source 542 is disposed at the position opposed to theside surface 51 c 4 and the side surface 52 c 4. According to thisconfiguration, it is possible for the present disclosure to realize thelight source device 2 small in size and capable of emitting the whitelight.

Further, in general, the light emitted from the LED is larger indiffusion angle compared to the light emitted form the semiconductorlaser. Therefore, the light source using the LED tends to be large inetendue determined by the product of the light emitting area of thelight source and the solid angle of the light from the light sourcecompared to the light source using the semiconductor laser. The increasein etendue of the light source device increases the light which cannotbe taken by the optical system in the posterior stage of the lightsource device to cause deterioration of the light use efficiency as theprojector. Therefore, when used as the light source device for theprojector, it is desirable for the etendue to be as small as possible.

From that point of view, in the case of the light source device 2according to the present embodiment, the light source 54 has the firstLED 61 and the second LED 62, and the light large in diffusion angleemitted from each of the LED enters the first wavelength conversion rod51 or the second wavelength conversion rod 52 from the side surfacelarge in area. Meanwhile, the composite light KW as the white light isemitted from the light exit end surface 65 c of the dichroic prism 65having the size corresponding to the end surface sufficiently small inarea compared to the side surfaces of the wavelength conversion rods 51,52. As described above, according to the present embodiment, it ispossible to substantively decrease the light emitting area, and thus itis possible to realize the light source device 2 small in etendue. As aresult, by using this light source device 2 in the projector 1, it ispossible to improve the light use efficiency in the optical system inthe posterior stage of the light source device 2.

In the case of the present embodiment, since the first fluorescence KBas the blue fluorescence is emitted from the first wavelength conversionrod 51, the second fluorescence KY as the yellow fluorescence is emittedfrom the second wavelength conversion rod 52, and the composite light KWas the white light is obtained by combining the first fluorescence KBand the second fluorescence KY with each other, it is possible to adjustthe white balance of the white light by adjusting the balance betweenthe light intensity of the first fluorescence KB and the light intensityof the second fluorescence KY. As a specific adjustment method of thewhite balance, it is also possible to adopt a configuration in which,for example, the light source device 2 is provided with sensors fordetecting the respective light intensities of the first fluorescence KBand the second fluorescence KY, and the control section 58 appropriatelyadjusts the electrical power to be supplied to the first LED 61 and thesecond LED 62 in accordance with the deviations of the respective lightintensities detected by the sensors from a standard value to therebyindividually control the intensity of the first excitation light El andthe intensity of the second excitation light E2.

In the light source device 2 according to the present embodiment, sincethe first LED 61 are disposed so as to be opposed to the side surface 51c 3 and the side surface 51 c 4 of the first wavelength conversion rod51, and the second LED 62 are disposed so as to be opposed to the sidesurface 52 c 3 and the side surface 52 c 4 of the second wavelengthconversion rod 52, it is possible to select the LED having the optimumexcitation wavelength band with respect to each of the wavelengthconversion rods 51, 52.

In the light source device 2 according to the present embodiment, sincethe angle conversion element 56 is disposed at the light exit side ofthe light combining section 55, it is possible to collimate thecomposite light KW emitted from the light combining section 55. Further,since the collimator lens 57 is disposed at the light exit side of theangle conversion element 56, it is possible to further improve theparallelism of the composite light KW. Thus, it is possible to improvethe light use efficiency in the optical system in the posterior stage ofthe light source device 2.

In the light source device 2 according to the present embodiment, sincethe mirror 63 is disposed on the second end surface 51 b of the firstwavelength conversion rod 51 and the fourth end surface 52 b of thesecond wavelength conversion rod 52, the first fluorescence KB and thesecond fluorescence KY can be prevented from being emitted from the sideof the second end surface 51 b and the fourth end surface 52 b. Thus, itis possible to improve the use efficiency of the first fluorescence KBand the second fluorescence KY.

It is also possible to dispose a reflecting film formed of, for example,a metal film between the side surface 51 c 1 of the first wavelengthconversion rod 51 and the side surface 52 c 1 of the second wavelengthconversion rod 52 instead of the gap (the air layer). It should be notedthat the light loss on the reflecting surface is smaller when disposingthe air layer between the two wavelength conversion rods. Therefore,when placing importance on the light loss, it is preferable to disposethe air layer.

Specifically, since the side surface 51 c 1 of the first wavelengthconversion rod 51 and the side surface 52 c 1 of the second wavelengthconversion rod 52 are opposed to each other via the air layer, thereflection of the light on the side surfaces 51 c 1, 52 c 1 of therespective wavelength conversion rods 51, 52 becomes the totalreflection not accompanied by the light loss. Thus, the light useefficiency can be improved. Further, it is desirable for each of theside surfaces of the respective wavelength conversion rods 51, 52 tosmoothly be polished. Thus, it is possible to further suppress the lightloss.

The projector 1 according to the present embodiment is equipped with thelight source device 2 described above, and is therefore excellent inlight use efficiency, and at the same time, reduction in size can beachieved.

It should be noted that it is also possible for the wavelengthconversion rods 51, 52 and the light source 54 in the present embodimentto have the configuration of the modified example described below.

Modified Example

FIG. 5 is a schematic configuration diagram of a light source device 22according to a modified example of the first embodiment. In FIG. 5, theconstituents common to those shown in FIG. 2 are denoted by the samereference numerals, and the description thereof will be omitted.

As shown in FIG. 5, in the light source device according to the modifiedexample, the first wavelength conversion rod 51 and a second wavelengthconversion rod 59 have respective dimensions different from each other.Specifically, the length in the longitudinal direction of the secondwavelength conversion rod 59 is longer than the length in thelongitudinal direction of the second wavelength conversion rod 52 of thefirst embodiment. Thus, the length in the longitudinal direction of thesecond wavelength conversion rod 59 is made longer than the length inthe longitudinal direction of the first wavelength conversion rod 51.The second wavelength conversion rod 59 has a third end surface 59 a anda fourth end surface 59 b opposed to each other, and side surfaces 59 c1, 59 c 2 crossing the third end surface 59 a and the fourth end surface59 b.

Further, the second LED 62 constituting the light source 64 is larger innumber than the first LED 61 due to the fact that the second wavelengthconversion rod 59 is longer than the first wavelength conversion rod 51.

The rest of the configuration of the light source device issubstantially the same as that of the embodiment described above.

It is also possible to adjust the white balance in the design phase ofthe light source device by adopting a measure of making the firstwavelength conversion rod 51 and the second wavelength conversion rod 59different in length, or a measure of making the first LED 61 and thesecond LED 62 different in number as in the light source device 22according to the modified example.

Second Embodiment

Hereinafter, a second embodiment of the present disclosure will bedescribed using FIG. 6.

A light source device according to the second embodiment issubstantially the same in basic configuration as that of the firstembodiment, but is different from that of the first embodiment in thepoint that a reflective polarization element is added. Therefore, thedescription of the overall configuration of the light source device willbe omitted.

FIG. 6 is a schematic configuration diagram of the light source device23 according to the second embodiment.

In FIG. 6, the constituents common to those shown in FIG. 2 are denotedby the same reference numerals, and the description thereof will beomitted.

As shown in FIG. 6, the light source device 23 according to the secondembodiment is provided with the first wavelength conversion rod 51, thesecond wavelength conversion rod 52, the light source 54, the lightcombining section 55, the angle conversion element 56, a reflectivepolarization plate 35 (the reflective polarization element), thecollimator lens 57 and the control section 58.

The reflective polarization plate 35 is disposed at the exit side of thelight combining section 55, and at the same time, on the light exit sideof the angle conversion element 56. The composite light KW emitted fromthe angle conversion element 56 is the light emitted from the phosphor,and has no particular polarization direction. The reflectivepolarization plate 35 transmits the light with a first polarizationdirection out of the composite light KW having no particularpolarization direction, and reflects the light with a secondpolarization direction different from the first polarization state. Itshould be noted that the light with the first polarization directioncoincides in polarization direction with the light emitted from thepolarization conversion element 32 shown in FIG. 1. Alternatively, whenusing the light source device 23 according to the present embodiment,since the polarization direction of the composite light KW is uniformedinto the first polarization direction, the projector 1 is not requiredto be provided with the polarization conversion element 32.

The rest of the configuration of the light source device 23 issubstantially the same as in the first embodiment.

Also in the second embodiment, it is possible to obtain substantiallythe same advantages as in the first embodiment such as the advantagethat it is possible to realize the compact light source device 23 foremitting the white light, and the advantage that it is possible torealize the light source device 23 small in etendue.

Further, in the light source device 23 according to the secondembodiment, the light with the second polarization direction having beenreflected by the reflective polarization plate 35 returns to the firstwavelength conversion rod 51 or the second wavelength conversion rod 52,and then reflected by the mirror 63 to enter the reflective polarizationplate 35 once again. On this occasion, since the polarization directionof the light having entered the reflective polarization plate 35 haschanged from the polarization direction of the light when firstreflected by the reflective polarization plate 35, at least a part ofthe light is transmitted through the reflective polarization plate 35.As described above, according to the light source device 23 related tothe second embodiment, it is possible to reuse the light with thepolarization direction having been reflected by the reflectivepolarization plate 35, and thus, it is possible to obtain the compositelight KW with the uniform polarization direction.

Further, the blue light out of the light having been reflected by thereflective polarization plate 35 is reflected by the dichroic mirror 65m to return to the first wavelength conversion rod 51, while the yellowlight is transmitted through the dichroic mirror 65 m to return to thesecond wavelength conversion rod 52. Therefore, there is no chance forthe blue light to enter the second wavelength conversion rod 52 to beconsumed by exciting the phosphor in the second wavelength conversionrod 52. Thus, according to the light source device 23 related to thesecond embodiment, there is obtained an advantage that the white balanceof the composite light KW is maintained in addition to the fact that thereuse of the polarized light is achieved.

Third Embodiment

A third embodiment of the present disclosure will hereinafter bedescribed using FIG. 7.

A light source device according to the third embodiment is substantiallythe same in basic configuration as that of the first embodiment, but isdifferent in the configuration of the light source from that of thefirst embodiment. Therefore, the description of the overallconfiguration of the light source device will be omitted.

FIG. 7 is a schematic configuration diagram of the light source device24 according to the third embodiment.

In FIG. 7, the constituents common to those shown in FIG. 2 are denotedby the same reference numerals, and the description thereof will beomitted.

As shown in FIG. 7, the light source device 24 according to the thirdembodiment is provided with the first wavelength conversion rod 51, thesecond wavelength conversion rod 52, a light source 36, the lightcombining section 55, the angle conversion element 56 and the collimatorlens 57.

The light source 36 is disposed at a position opposed to one sidesurface of each of the wavelength conversion rods 51, 52. It should benoted that it is also possible to further add a light source at aposition opposed to another side surface of each of the wavelengthconversion rods 51, 52 in addition to the light source 36.

The light source 36 is provided with a substrate 543, and a plurality ofLED 67 mounted on a surface of the substrate 543, the surface beingopposed to the first wavelength conversion rod 51 and the secondwavelength conversion rod 52. In the present embodiment, the lightsource 36 is provided with the 6 LED 67, but the number of the LED 67 isnot particularly limited. Each of the LED 67 emits the excitation lightin the excitation wavelength band. The excitation wavelength band is theultraviolet wavelength band of, for example, 200 nm through 380 nm. Itshould be noted that the excitation wavelength band can also be a violetwavelength band of, for example, around 400 nm.

Each of the LED 67 is disposed so as to be opposed to both of the firstwavelength conversion rod 51 and the second wavelength conversion rod52. In other words, one LED is disposed so as to straddle the firstwavelength conversion rod 51 and the second wavelength conversion rod52, and functions as both of the light source for the excitation lightwhich is made to enter the first wavelength conversion rod 51 and thelight source for the excitation light which is made to enter the secondwavelength conversion rod 52. Therefore, the excitation light in thesame excitation wavelength band enters the first wavelength conversionrod 51 and the second wavelength conversion rod 52. In the presentembodiment, out of the excitation light emitted from the LED 67, theexcitation light entering the first wavelength conversion rod 51corresponds to the first excitation light, and the excitation lightentering the second wavelength conversion rod 52 corresponds to thesecond excitation light.

The rest of the configuration of the light source device 24 issubstantially the same as in the first embodiment.

Also in the third embodiment, it is possible to obtain substantially thesame advantages as in the first embodiment such as the advantage that itis possible to realize the compact light source device 24 for emittingthe white light, and the advantage that it is possible to realize thelight source device 24 small in etendue.

Further, since each of the LED 67 is used by both of the firstwavelength conversion rod 51 and the second wavelength conversion rod52, the number of the LED 67 can be reduced, and the configuration ofthe light source 36 can be simplified.

Fourth Embodiment

A fourth embodiment of the present disclosure will hereinafter bedescribed using FIG. 8.

A light source device according to the fourth embodiment issubstantially the same in basic configuration as that of the firstembodiment, but is different in the configuration of the wavelengthconversion rods and the light source from that of the first embodiment.Therefore, the description of the overall configuration of the lightsource device will be omitted.

FIG. 8 is a schematic configuration diagram of the light source device25 according to the fourth embodiment.

In FIG. 8, the constituents common to those shown in FIG. 2 are denotedby the same reference numerals, and the description thereof will beomitted.

As shown in FIG. 8, the light source device 25 according to the fourthembodiment is provided with the first wavelength conversion rod 51, asecond wavelength conversion rod 72, a third wavelength conversion rod73, a light source 37, a light combining section 38, the angleconversion element 56 and the collimator lens 57.

The first wavelength conversion rod 51 and the second wavelengthconversion rod 72 are disposed at a distance in an orientation in whichthe side surface 51 c 1 of the first wavelength conversion rod 51 and aside surface 72 c 1 of the second wavelength conversion rod 72 areopposed to each other. The second wavelength conversion rod 72 and thethird wavelength conversion rod 73 are disposed at a distance in anorientation in which a side surface 72 c 2 of the second wavelengthconversion rod 72 and a side surface 73 c 1 of the third wavelengthconversion rod 73 are opposed to each other.

The light source 37 is disposed at a position opposed to one sidesurface of each of the wavelength conversion rods 51, 72 and 73. Itshould be noted that it is also possible to further add a light sourceat a position opposed to another side surface of each of the wavelengthconversion rods 51, 72 and 73 in addition to the light source 37.

The light source 37 is provided with the substrate 543, and a pluralityof LED 61, 82 and 83 mounted on a surface of the substrate 543, thesurface being opposed to the first wavelength conversion rod 51, thesecond wavelength conversion rod 72, and the third wavelength conversionrod 73. In the present embodiment, the light source 37 is provided withthe 18 LED 61, 82 and 83 in total, but the number of the LED 61, 82 and83 is not particularly limited. The LED 61, 82 and 83 emit the firstexcitation light, the second excitation light and third excitationlight, respectively. It should be noted that the light source 37 canalso have other optical members such as a light guide plate, a diffusionplate or a lens besides the substrate 543 and the LED 61, 82 and 83.

The plurality of LED 61, the plurality of LED 82 and the plurality ofLED 83 are disposed so as to be opposed to the side surface of the firstwavelength conversion rod 51, the side surface of the second wavelengthconversion rod 72 and the side surface of the third wavelengthconversion rod 73, respectively. As shown in FIG. 8, the plurality ofLED 61, the plurality of LED 82 and the plurality of LED 83 are arrangedin three columns. Some (six) LED 61 are arranged along the longitudinaldirection of the first wavelength conversion rod 51, other (six) LED 82are arranged along the longitudinal direction of the second wavelengthconversion rod 72, and still other (six) LED 83 are arranged along thelongitudinal direction of the third wavelength conversion rod 73.Hereinafter, the LED arranged along the longitudinal direction of thefirst wavelength conversion rod 51 are referred to as first LED 61, theLED arranged along the longitudinal direction of the second wavelengthconversion rod 72 are referred to as second LED 82, and the LED arrangedalong the longitudinal direction of the third wavelength conversion rod73 are referred to as third LED 83.

The first excitation light for exciting the first phosphor included inthe first wavelength conversion rod 51 is emitted form the first LED 61.The second excitation light for exciting the second phosphor included inthe second wavelength conversion rod 72 is emitted form the second LED82. The second excitation light for exciting third phosphor included inthe third wavelength conversion rod 73 is emitted form the third LED 83.As described above, the first excitation light, the second excitationlight and the third excitation light are different in phosphor to excitefrom each other. Therefore, it is possible for the first LED 61, thesecond LED 82 and the third LED 83 to emit light in respectiveexcitation wavelength bands which are optimized for the phosphors of therespective wavelength conversion rods 51, 72 and 73, and are thereforedifferent from each other, or emit light in the same excitationwavelength band commonly used as the excitation light for all of thephosphors.

In the present embodiment, the first LED 61 are disposed so as to beopposed to the side surfaces of the first wavelength conversion rod 51,and emit the first excitation light in the first excitation wavelengthband toward the side surface. The first excitation wavelength band isthe ultraviolet wavelength band of, for example, 200 nm through 380 nm.It should be noted that the first excitation wavelength band can also bea violet wavelength band of, for example, around 400 nm.

The second LED 82 are disposed so as to be opposed to the side surfaceof the second wavelength conversion rod 72, and emit the secondexcitation light in the second excitation wavelength band toward theside surface. The second excitation wavelength band is the bluewavelength band of, for example, 450 nm through 495 nm. It should benoted that the second excitation wavelength band can also be theultraviolet wavelength band of, for example, 200 nm through 380 nm, orcan also be the violet wavelength band around 400 nm.

The third LED 83 are disposed so as to be opposed to the side surface ofthe third wavelength conversion rod 73, and emit the third excitationlight in a third excitation wavelength band toward the side surface. Thethird excitation wavelength band is the blue wavelength band of, forexample, 450 nm through 495 nm. It should be noted that the thirdexcitation wavelength band can also be the ultraviolet wavelength bandof, for example, 200 nm through 380 nm, or can also be the violetwavelength band around 400 nm.

The first wavelength conversion rod 51 converts the first excitationlight into first fluorescence KB (blue light) in a first wavelengthband. The first wavelength band is the blue wavelength band of, forexample, 450 through 495 nm. The first wavelength conversion rod 51 isformed of, for example, fluorescent glass obtained by dispersingrare-earth ions in the glass, or a material obtained by dispersing bluephosphor in a binder such as glass or resin. Specifically, as thefluorescent glass, there is used Lumilass (a trade name; made by SumitaOptical Glass, Inc.) or the like. As the blue phosphor (a firstphosphor), there is used, for example, BaMgAl₁₀O₁₇: Eu (II).

The second wavelength conversion rod 72 converts the second excitationlight into second fluorescence KG (green light) in a second wavelengthband. The second wavelength band is a green wavelength band of, forexample, 500 through 570 nm. The second wavelength conversion rod 72includes the phosphor material such as a Lu₃Al₅O₁₂:Ce³⁺ phosphor, aY₃O₄:Eu²⁺ phosphor, a (Ba,Sr)₂SiO₄:Eu²⁺ phosphor, a Ba₃Si₆O₁₂N₂:Eu²⁺phosphor or a (Si,Al)₆(O,N)₈:Eu²⁺ phosphor as a green phosphor (a secondphosphor).

The third wavelength conversion rod 73 converts the third excitationlight into third fluorescence KR (red light) in a third wavelength band.The third wavelength band is a red wavelength band of, for example, 600through 800 nm. The third wavelength conversion rod 73 includes, forexample, the YAG phosphor (any one of Pr:YAG, Eu:YAG and Cr:YAG) made of(Y_(1-x),Gd_(x))₃ (Al, Ga)₅ O₁₂ having any one of Pr, Eu and Crdispersed as an activator agent as a red phosphor (a third phosphor). Itshould be noted that it is possible for the activator agent to include aspecies selected from Pr, Eu and Cr, or to be a coactivation typeactivator agent including two or more species selected from Pr, Eu andCr.

The first wavelength conversion rod 51 has the mirror disposed on thesecond end surface 51 b of the first wavelength conversion rod 51. Thesecond wavelength conversion rod 72 has the mirror 63 disposed on afourth end surface 72 b of the second wavelength conversion rod 72. Thethird wavelength conversion rod 73 has the mirror 63 disposed on a sixthend surface 73 b of the third wavelength conversion rod 73. In thepresent embodiment, the mirror 63 common to all of the first wavelengthconversion rod 51, the second wavelength conversion rod 72 and the thirdwavelength conversion rod 73 is disposed, but the mirror 63 can also beprovided individually to each of the wavelength conversion rods. Themirror 63 is formed of a metal film or a dielectric multilayer filmformed on the end surface of each of the wavelength conversion rods 51,72 and 73.

The light combining section 38 is provided with a first prism 41, asecond prism 42 and a dichroic prism 43. The light combining section 38combines the first fluorescence KB, the second fluorescence KG and thethird fluorescence KR with each other.

The first prism 41 is disposed on the first end surface 51 a of thefirst wavelength conversion rod 51. The first prism 41 reflects thefirst fluorescence KB (the blue light), which has been emitted from thefirst end surface 51 a of the first wavelength conversion rod 51, with areflecting surface 41 f to thereby fold the light path as much as 90°,and then emits the first fluorescence KB from a light exit end surface41 b.

The second prism 42 is disposed on a fifth end surface 73 a of the thirdwavelength conversion rod 73. The second prism 42 reflects the thirdfluorescence KR (the red light), which has been emitted from the fifthend surface 73 a of the third wavelength conversion rod 73, with areflecting surface 42 f to thereby fold the light path as much as 90°,and then emits the third fluorescence KB from a light exit end surface42 b.

The dichroic prism 43 is disposed so as to be opposed to the light exitend surface 41 b of the first prism 41, the light exit end surface 42 bof the second prism 42 and the third end surface 72 a of the secondwavelength conversion rod 72. The dichroic prism 43 has a first dichroicmirror 43 m 1 and a second dichroic mirror 43 m 2 crossing each other.The first dichroic mirror 43 m 1 reflects the first fluorescence KB (theblue light) and transmits the second fluorescence KG (the green light)and the third fluorescence KR (the red light). The second dichroicmirror 43 m 2 reflects the third fluorescence KR (the red light) andtransmits the first fluorescence KB (the blue light) and the secondfluorescence KG (the green light). Thus, the dichroic prism 43 combinesthe first fluorescence KB emitted from the first wavelength conversionrod 51, the second fluorescence KG emitted from the second wavelengthconversion rod 72 and the third fluorescence KR emitted from the thirdwavelength conversion rod 73 with each other to emit the composite lightKW.

The rest of the configuration of the light source device 25 issubstantially the same as in the first embodiment.

Also in the fourth embodiment, it is possible to obtain substantiallythe same advantages as in the first embodiment such as the advantagethat it is possible to realize the compact light source device 25 foremitting the white light, and the advantage that it is possible torealize the light source device 25 small in etendue.

It should be noted that it is also possible for the light source device25 to be provided with a control section for individually controllingthe intensity of the first excitation light emitted from the first LED61, the intensity of the second excitation light emitted from the secondLED 82, and the intensity of the third excitation light emitted from thethird LED 83. According to this configuration, by the control sectionappropriately adjusting the light intensities of the first fluorescence(the blue light), the second fluorescence (the green light) and thethird fluorescence (the red light), it is possible to adjust the whitebalance of the composite light KW.

It should be noted that the scope of the present disclosure is notlimited to the embodiments described above, but a variety ofmodifications can be provided thereto within the scope or the spirit ofthe present disclosure.

For example, there is cited the example in which the wavelengthconversion rod includes the phosphor for emitting the yellowfluorescence in the first embodiment described above, it is alsopossible for the wavelength conversion rod to include two types ofphosphor consisting of the phosphor for emitting the green fluorescenceand the phosphor for emitting the red fluorescence. In that case, it ispossible for the two types of phosphor to be homogenously mixed insidethe wavelength conversion rod, or to be eccentrically located inseparate areas.

Further, the dichroic prism constituting the light combining section canbe reversed in the relationship between the reflected light and thetransmitted light from the first through third embodiments describedabove. In other words, it is possible for the light combining section tobe provided with a dichroic prism having a dichroic mirror fortransmitting the first fluorescence (the blue light) emitted from thefirst wavelength conversion rod and reflecting the second fluorescence(the yellow light) emitted from the second wavelength conversion rod. Inthis case, the dichroic prism is disposed on the first end surface ofthe first wavelength conversion rod, and the prism for bending the lightpath is disposed on the first end surface of the second wavelengthconversion rod.

Further, in each of the embodiments described above, it is also possibleto dispose a dichroic mirror for reflecting the first excitation lightand transmitting the first fluorescence on the first end surface of thefirst wavelength conversion rod. Similarly, it is also possible todispose a dichroic mirror for reflecting the second excitation light andtransmitting the second fluorescence on the third end surface of thesecond wavelength conversion rod. Similarly, in the fourth embodiment,it is possible to dispose a dichroic mirror for reflecting the thirdexcitation light and transmitting the third fluorescence on the fifthend surface of the third wavelength conversion rod. According to theseconfigurations, it is possible to improve the wavelength conversionefficiency in each of the wavelength conversion rods. Further, it isalso possible to dispose a dichroic mirror for transmitting theexcitation light and reflecting the fluorescence on the side surface ofeach of the wavelength conversion rods.

Although in the embodiments described above, there is cited the exampleof the light source device for emitting the white light, the presentdisclosure can also be applied to a light source device for emittingother colored light than the white light. For example, it is alsopossible to configure a light source device which is provided with awavelength conversion rod for emitting the green light and a wavelengthconversion rod for emitting the red light, and emits the yellow light.Even in that case, according to the present disclosure, it is possibleto realize a compact light source device for emitting the yellow light.

Although in the embodiments described above, there is proposed theexample of using the dichroic prism as the light combining section, itis also possible to apply other optical members capable of performinglight composition. For example, a scattering body having a lightscattering structure inside can also be used as the light combiningsection. As an example of the scattering body, there can be cited glassincluding scattering particles, an optical member including ananisotropic scattering layer, and so on.

Further, the specific configurations such as the shape, the number, thearrangement, and the material of each of the constituents constitutingthe light source device are not limited to those of the embodimentsdescribed above, but can arbitrarily be modified.

Although in the first embodiment described above, there is described anexample when applying the present disclosure to the transmissive liquidcrystal projector, the present disclosure can also be applied to areflective liquid crystal projector. Here, “transmissive” means that theliquid crystal light valve including the liquid crystal panel and so onhas a configuration of transmitting the light. The term “reflective”means that the liquid crystal light valve has a configuration ofreflecting the light.

Although in the first embodiment described above, there is cited theexample of the projector using three liquid crystal panels, the presentdisclosure can also be applied to a projector using one liquid crystallight valve alone or a projector using four or more liquid crystal lightvalves.

Although in the embodiments described above, there is described theexample of installing the light source device according to the presentdisclosure in the projector, this is not a limitation. The light sourcedevice according to the present disclosure can also be applied tolighting equipment, a headlight of a vehicle, and so on.

What is claimed is:
 1. A light source device comprising: a light sourceconfigured to emit first excitation light and second excitation light; afirst wavelength conversion section including a first phosphor, andconfigured to convert the first excitation light into first fluorescencehaving a first wavelength band different from a wavelength band of thefirst excitation light; a second wavelength conversion section includinga second phosphor, and configured to convert the second excitation lightinto second fluorescence having a second wavelength band different froma wavelength band of the second excitation light and the firstwavelength band; and a light combining section configured to combine thefirst fluorescence emitted from the first wavelength conversion sectionand the second fluorescence emitted from the second wavelengthconversion section with each other, wherein the first wavelengthconversion section has a first end surface and a second end surfaceopposed to each other, and a first side surface crossing the first endsurface and the second end surface, the second wavelength conversionsection has a third end surface and a fourth end surface opposed to eachother, and a second side surface crossing the third end surface and thefourth end surface, the first side surface of the first wavelengthconversion section and the second side surface of the second wavelengthconversion section are opposed to each other, the first fluorescence isemitted from the first end surface of the first wavelength conversionsection toward the light combining section, and the second fluorescenceis emitted from the third end surface of the second wavelengthconversion section toward the light combining section.
 2. The lightsource device according to claim 1, wherein the first wavelengthconversion section has a third side surface crossing the first endsurface and the second end surface, the second wavelength conversionsection has a fourth side surface crossing the third end surface and thefourth end surface, the first excitation light enters the firstwavelength conversion section from the third side surface of the firstwavelength conversion section, and the second excitation light entersthe second wavelength conversion section from the fourth side surface ofthe second wavelength conversion section.
 3. The light source deviceaccording to claim 2, wherein the light source includes a first lightemitting diode disposed so as to be opposed to the third side surface ofthe first wavelength conversion section, and configured to emit thefirst excitation light, and a second light emitting diode disposed so asto be opposed to the fourth side surface of the second wavelengthconversion section, and configured to emit the second excitation light.4. The light source device according to claim 3, further comprising: acontrol section configured to individually control an intensity of thefirst excitation light to be emitted from the first light emitting diodeand an intensity of the second excitation light emitted from the secondlight emitting diode.
 5. The light source device according to claim 1,wherein the light combining section includes a dichroic prism providedto one of the first end surface of the first wavelength conversionsection and the third end surface of the second wavelength conversionsection, and having a dichroic mirror configured to reflect one of thefirst fluorescence and the second fluorescence and transmit the other ofthe first fluorescence and the second fluorescence, and a prism providedto the other of the first end surface of the first wavelength conversionsection and the third end surface of the second wavelength conversionsection, and having a reflecting surface configured to reflect one ofthe first fluorescence and the second fluorescence toward the dichroicprism.
 6. The light source device according to claim 5, wherein thedichroic prism has contact with the third end surface of the secondwavelength conversion section.
 7. The light source device according toclaim 5, wherein the prism has contact with the first end surface of thefirst wavelength conversion section.
 8. The light source deviceaccording to claim 1, wherein the first side surface of the firstwavelength conversion section and the second side surface of the secondwavelength conversion section are opposed to each other via an airlayer.
 9. The light source device according to claim 1, wherein thefirst wavelength band is a blue wavelength band, and the secondwavelength band is a yellow wavelength band.
 10. The light source deviceaccording to claim 1, further comprising: a third wavelength conversionsection including a third phosphor, and configured to emit thirdfluorescence having a third wavelength band different from the firstwavelength band and the second wavelength band, wherein the lightcombining section combines the first fluorescence, the secondfluorescence and the third fluorescence with each other.
 11. The lightsource device according to claim 10, wherein the light source emitsthird excitation light, and the third wavelength conversion sectionconverts the third excitation light into the third fluorescence havingthe third wavelength band different from a wavelength band of the thirdexcitation light.
 12. The light source device according to claim 10,wherein the first wavelength band is a blue wavelength band, the secondwavelength band is a green wavelength band and the third wavelength bandis a red wavelength band.
 13. The light source device according to claim1, further comprising: an angle conversion element which is disposed ata light exit side of the light combining section, which includes an endsurface of incidence of light and a light exit end surface, and whichmakes a diffusion angle in the light exit end surface smaller than adiffusion angle in the end surface of incidence of light.
 14. The lightsource device according to claim 1, further comprising: a reflectivepolarization element disposed at a light exit side of the lightcombining section, and configured to transmit light with a firstpolarization direction and reflect light with a second polarizationdirection different from the first polarization direction.
 15. A lightsource device comprising: a light source configured to emit light; afirst wavelength conversion section including a first phosphor, andconfigured to convert the light emitted from the light source into firstfluorescence, and emit the first fluorescence from a first light exitsurface; a second wavelength conversion section disposed in parallel tothe first wavelength conversion section, including a second phosphor,and configured to convert the light emitted from the light source intosecond fluorescence, and emit the second fluorescence from a secondlight exit surface; a prism disposed so as to be opposed to the firstlight exit surface, and configured to reflect the first fluorescenceemitted from the first wavelength conversion section; and a dichroicprism disposed so as to be opposed to the prism and the second lightexit surface, and configured to combine the first fluorescence emittedfrom the prism and the second fluorescence emitted from the secondwavelength conversion section with each other to emit light obtained bycombining the first fluorescence and the second fluorescence with eachother, wherein the first fluorescence and the second fluorescence aredifferent in wavelength band from each other.
 16. A projectorcomprising: the light source device according to claim 1; a lightmodulation device configured to modulate light from the light sourcedevice in accordance with image information; and a projection opticaldevice configured to project the light modulated by the light modulationdevice.